Abrading Disc

ABSTRACT

A rotating circular disc attaches to a rotary motion abrading tool and converts the rotary motion to a random orbital motion. The disc has a center and has an axis of rotation that is off center and that forms a center of gravity. One embodiment of the disc is a backing plate. A second embodiment of the disc is a polishing pad. A third embodiment of the disc is a combination of a backing plate and a polishing pad.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser. No. 62/192,198, Jul. 14, 2015.

FIELD OF THE INVENTION

This invention relates to abrading. More particularly, this invention relates to backing plates and pads for stone polishers and other rotary disk tools.

BACKGROUND OF THE INVENTION

Abrading is the shaping and smoothing of materials with abrasives. Abrading is also known as polishing, sanding, or buffing depending on the material being treated and the finish desired. These terms are used interchangeably herein. Abrading is usually performed manually for smaller operations. However, electrically powered rotary tools with abrading discs are commonly used for larger scale operations. The abrading disc typically consists of a replaceable abrasive polishing pad attached to a metal backing plate. The term “abrading disc” is used herein to refer to the polishing pad, the backing plate, or the combination as the context requires. The backing plate and polishing pad have centers that form both the axis of rotation and the center of gravity so that the rotation is smooth and vibrations are minimized.

A wide variety of abrasives are used. Abrasives made of aluminum oxide, silicon carbide, garnet, and emery are commonly used for sanding woods and metals. Abrasives made of harder materials such as diamond are commonly used for polishing materials such as stone (e.g., granite and marble), quartz, glass, and concrete. Abrasives made of softer materials such as wool, cotton, and other fabrics are commonly used for polishing metals and plastics.

Rotary motion abrading tools in which the abrasive polishing pad travels in a circular motion can cause gouging in the material being treated because the abrasive pad repeatedly travels in the same path. Random orbital motion abrading tools move the abrasive pad in an elliptical motion as they simultaneously rotate in a circular motion. The random orbital motion ensures that no single part of the abrasive pad travels in the same path twice. Random orbital motion abrading tools contain multiple rotating members that rotate about different axes. Random orbital tools are disclosed in McLain, U.S. Pat. No. 5,687,442, Nov. 18, 1997, and Lampka et al., U.S. Pat. No. 7,713,110, May 11, 2010. Random orbital tools have become preferred for fine abrading.

Large stone polishing machines are commonly used for finishing large stone surfaces such as countertops. Some of these machines have an externally threaded post for the attachment of a backing plate. Other machines have an opening (also referred to a chuck) into which an arbor (also referred to a spindle) connected to a circular backing plate holding a replaceable circular polishing pad is inserted. The term “arbor” is used herein to refer to the backing plate structure that attaches to the rotary tool and that forms the axis of rotation. Polishing stone generates large amounts of heat that can damage the tool and the stone. To both cool and lubricate, these polishing machines apply water to the surface being polished. The water is typically supplied by a water lines through the chuck and arbor. The necessity of the water line makes it impractical to incorporate multiple rotating members to provide random orbital motion.

Accordingly, there is a demand for a backing plate and polishing pad for a stone polisher and other rotary motion abrading tools that provide vibration-free random orbital motion without the need for multiple rotating members.

SUMMARY OF THE INVENTION

The general object of this invention is to provide an improved backing plate and polishing pad for a rotary motion abrading tool. A more particular object is to provide a backing plate and polishing pad that provide random orbital motion without the need for multiple rotating members.

I have invented an abrading disc for attachment to a rotary motion abrading tool that converts the rotary motion to a random orbital motion. The disc has a center, an axis of rotation that is off center and that forms a center of gravity, and a means for attachment to a rotary motion tool. One embodiment of the disc is a backing plate, a second embodiment of the disc is a polishing pad, and a third embodiment of the disc is a combination of a backing plate and a polishing pad.

I have also invented a backing plate for a rotary motion abrading tool that converts the rotary motion to a random orbital motion. The backing plate comprises a circular plate having a center, a working face for attachment of a circular pad, and an opposed face with an arbor extending outwardly from the opposed face that defines an axis of rotation. The axis of rotation is off center and forms a center of gravity when a circular polishing pad is attached to the working face.

I have also invented an assembly for a rotary motion abrading tool that converts the rotary motion to a random orbital motion. The assembly comprises: (a) a backing plate comprising a circular plate having a center, a working face for attachment of a circular polishing pad, an opposed face with an arbor extending outwardly from the opposed face that defines an axis of rotation, the axis of rotation being off center; and (b) a circular polishing pad attached to the working face of the backing plate, the circular pad being of substantially the same size as the working face, wherein the assembly has a center of gravity that is on the axis of rotation.

The disc of this invention provides vibration-free random orbital motion to a rotary motion tool without the need for multiple rotating members. It is especially suited for use with stone polishers having a water line through the chuck, both as the backing plate and as the polishing pad.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first embodiment of the backing plate of this invention.

FIG. 2 is a side elevation view thereof.

FIG. 3 is a top plan view thereof.

FIG. 4 is a top plan view of a second embodiment of the backing plate of this invention.

FIG. 5 is a perspective view thereof.

FIG. 6 is a perspective view of a third embodiment of the backing plate of this invention.

FIG. 7 is a side elevation view thereof.

FIG. 8 is a top plan view thereof.

FIG. 9 is a top plan view of a first embodiment of a polishing pad for use with the backing plate of this invention.

FIG. 10 is a top plan view of a second embodiment of a polishing pad for use with the backing plate of this invention.

FIG. 11 is a top plan view of a third embodiment of a polishing pad for use with the backing plate of this invention.

DETAILED DESCRIPTION OF THE INVENTION

1. The Invention in General

The invention is an abrading disc having an axis of rotation that is off center and that forms the center of gravity. One embodiment of the invention is a backing plate, a second embodiment is a polishing pad, and a third embodiment is a combination of a backing plate and a polishing pad. Referring first to FIGS. 1 to 3, a first embodiment of the backing plate 10 of this invention is similar to a conventional backing plate with two exceptions. First, the arbor for attachment to a rotary motion abrading tool is off center as best seen in FIG. 3. Second, mass is removed from a portion of the backing plate so that the center of gravity is on the axis of rotation. Having the center of gravity on the axis of rotation enables the backing plate to rotate without vibration. The backing plate and polishing pad are discussed in more detail below.

2. The Backing Plate

As discussed above, one aspect of this invention is a backing plate. The backing plate is a circular plate with two faces. A working face 11 faces the work piece (not shown) and is adapted to receive a circular polishing pad, described in detail below. The working face preferably has a permanently attached piece of hook and loop fabric, either the hook side or the loop side. The polishing pad preferably has a mating piece of hook and loop fabric for temporary and secure attachment. The opposed face 12 has an arbor 13 that extends outwardly. The arbor is attached to a threaded post, chuck or other structure in a rotary motion tool (not shown). In the embodiment shown, the arbor is an internally threaded semi-cylindrical extension with two flat sides for engagement of a wrench or other tightening tool.

The center 14 of the arbor defines the axis of rotation of the backing plate. The arbor (and the axis of rotation) are located off center. In other words, the center of the arbor is spaced apart from the center 15 of the backing plate. The distance between the center of the arbor and the center of the backing plate is generally about 0.05 to 0.2 times the diameter of the backing plate and is preferably about 0.1 to 0.15 times the diameter of the backing plate. In the preferred embodiment, the backing plate has a diameter of about four inches and the distance between center of the arbor and the center of the backing plate is about one-half inch.

The axis of rotation defined by the center of the arbor forms the center of gravity of the plate. Locating the center of gravity at the axis of rotation minimizes unwanted vibration. For the center of gravity to be located off center in a circular plate, mass must be distributed non-uniformly. In the preferred embodiment, a crescent shaped recess 16 is formed in the opposing face of the plate. A geometric crescent is the shape produced when a circular disk has a segment from another circle with a different center removed from its edge, so that what remains is a shape enclosed by two circular arcs of similar diameters which intersect at two points. The term “crescent” is used herein to refer to shapes that are the same as or similar to the exact geometric shape. It is also understood by those skilled in the art that other non-uniform mass distributions are feasible, but are more difficult to machine.

A second embodiment 110 of the backing plate is shown in FIGS. 4 and 5. The second embodiment differs from the first embodiment in that the arbor is on a raised circular platform 118.

A third embodiment 210 of the backing plate is shown in FIGS. 6 to 8. The third embodiment differs from the second embodiment in that the center of gravity is located exactly on the axis of rotation only when a conventional polishing pad with a uniform weight distribution is attached. The third embodiment also differs in that the crescent shaped recess is rounded where the two circular arcs meet and in that the raised platform 218 is cone shaped rather than circular.

The size of the backing plate is a matter of choice that depends on the rotary tool with which it will be used. The backing plate generally has a diameter of about three to twelve inches. The depth of the backing plate is generally about one-quarter to one inch. The backing plate is generally made of metal such as steel or aluminum.

3. The Polishing Pad

As discussed above, a second aspect of this invention is a polishing pad 20 with a non-uniform weight distribution. The polishing pad is used with the first or second embodiments of the backing plate and is attached to the working face of the backing plate. The attachment is preferably removable so that the backing plate can be reused with replaceable polishing pads. However, if desired the attachment can be permanent. As previously discussed, the pad is preferably removably attached to the plate using hook and loop fabric. However, clamps, screws, and the like are also suitable for attachment. The polishing pad is of substantially the same diameter as the working face. The polishing pad has a non-uniform mass distribution so that its center of gravity is on the same axes of rotation as the rotary tool and the backing plate when attached to the backing plate.

To ensure that the polishing pad is properly aligned, markings or other guides are placed on both the backing plate and the pad. The use of markings is shown in FIGS. 4 and 9 where markings 117 on the perimeter of the backing plate are aligned with markings 21 on the perimeter of the polishing pad.

The working face of the polishing pad contains an abrasive that is suited for the material to be polished. For example, a resin bonded diamond surface is preferred for polishing hard materials such as granite, marble, quartz, glass, concrete, and the like.

Three embodiments of polishing pads with centers of gravity that are off center are shown in FIGS. 9 to 11. As previously mentioned, the centers of gravity of the polishing pads are on the same axes of rotation as the rotary tool and the backing plate when attached. In FIG. 9, the first embodiment 20 of the polishing pad contains a plurality of raised circular nubs containing the abrasive. The nubs are non-uniformly distributed to form the center of gravity in the center of the empty circle.

In FIG. 10, the second embodiment 120 contains raised square nubs containing the abrasive. The nubs are shown extending in only four directions for illustration purposes. The nubs would be distributed on the entire surface. In FIG. 7, the nubs are equally spaced and are of varying mass so that the center of gravity is located off center. The position of the crescent shaped recess of the backing plate is shown in phantom lines for illustration purposes.

In FIG. 11, the third embodiment 220 contains raised square nubs containing the abrasive. The nubs are shown extending in only four directions for illustration purposes. The nubs are of the same mass and are unevenly distributed so that the center of gravity is located off center. The position of the crescent shaped recess of the backing plate is shown in phantom lines for illustration purposes.

As previously discussed, the third embodiment of the backing plate shown in FIGS. 6 to 8 uses a conventional, uniformly-weighted polishing pad.

4. Uses

The use of the backing plate and polishing pad can now be considered. The backing plate is connected to a conventional rotary tool in a conventional way. For example, rotary stone polishers typically contain a male threaded member. A backing plate with an internally threaded arbor is attached to the member using a wrench or the like. A polishing pad is then attached. As discussed above, the combination of the backing plate and the polishing pad has a center of gravity that is on exactly the same axes of rotation as the rotary tool. The rotary tool is then used in a conventional manner.

The backing plate and polishing pad are especially useful with countertop polishing machines, with or without a center water feed, in the construction industry. They are also useful with other polishing machines in the automotive, marine, and aerospace industries.

5. Advantages

The backing plate and polishing pad have many advantages over prior art rotary tools. They move in a random orbital motion with minimal vibration. This motion enables very fine polishing to be accomplished without the swirls, dips, and divots typically caused by a rotary motion. They are faster and less tiring to the operator. They provide longer life to the polishing pad. They are also safer because they are less likely to “catch” on the surface being polished and cause the tool to be jerked or thrown.

The backing plate and polishing pad of this invention also have many advantages over prior art random orbital motion tools. They provide random orbital motion without the complex cams, gearings, bearings, and other mechanical parts of the prior art tools. They work well in harsh environments and are not impaired by water, dust, or sludge. Applied pressure does not cause stalling.

The third embodiment of the backing plate has the further advantage of being compatible with conventional polishing pads having a uniform weight distribution, thus eliminating the requirement of using specialized polishing pads. 

I claim:
 1. An abrading disc for attachment to a rotary motion abrading tool that converts the rotary motion to a random orbital motion, the disc having a center, an axis of rotation that is off center and that forms a center of gravity, and a means for attachment to a rotary motion abrading tool.
 2. The abrading disc of claim 1 wherein the disc comprises a backing plate having a working face for attachment of a polishing pad and an opposed face with an arbor extending outwardly from the opposed face that defines the axis of rotation and that attaches to a rotary motion abrading tool.
 3. The abrading disc of claim 1 wherein the backing plate has a crescent shaped recess in the opposed face.
 4. The abrading disc of claim 1 wherein the disc comprises a polishing pad having a working face with an abrasive surface and an opposed face having a means for attachment to a backing plate.
 5. The abrading disc of claim 1 wherein the means for attachment comprises a hook and loop fabric.
 6. A backing plate for a rotary motion abrading tool that converts the rotary motion to a random orbital motion, the backing plate comprising a circular plate having a center, a working face for attachment of a circular polishing pad, an opposed face with an arbor extending outwardly from the opposed face that defines an axis of rotation, the axis of rotation being off center and forming a center of gravity when a circular polishing pad is attached to the working face.
 7. The backing plate of claim 6 wherein the opposed face has a crescent shaped recess.
 8. The backing plate of claim 6 wherein the working face comprises a hook and loop fabric.
 9. The backing plate of claim 6 wherein the axis of rotation forms the center of gravity when a circular polishing pad with a uniform weight distribution is attached.
 10. The backing plate of claim 6 wherein the axis of rotation forms the center of gravity when a circular polishing pad with a non-uniform weight distribution is attached.
 11. An assembly for a rotary motion abrading tool that converts the rotary motion to a random orbital motion, the assembly comprising: (a) a backing plate comprising a circular plate having a center, a working face for attachment of a circular polishing pad, an opposed face with an arbor extending outwardly from the opposed face that defines an axis of rotation, the axis of rotation being off center; and (b) a circular polishing pad attached to the working face of the backing plate, the pad being of substantially the same size as the working face; wherein the assembly has a center of gravity that is on the axis of rotation.
 12. The assembly of claim 11 wherein the working face of the backing plate comprises a hook and loop fabric.
 13. The assembly of claim 11 wherein the opposed face of the backing plate comprises a crescent shaped recess.
 14. The assembly of claim 11 wherein the opposed face of backing plate comprises an arbor on a cone shaped platform.
 15. The assembly of claim 11 wherein the polishing pad has a uniform weight distribution. 